1. Field of the Invention
The present invention relates to an optical composite transceiver for a local area network (hereinafter, LAN) system using an optical fiber cable.
2. Description of the Related Art
Conventionally, the LAN system is classified into three types, i.e., a bus type, a ring type, and a star type, according to the connection of interfaces in the network. The present invention relates to the bus type LAN system. The LAN system has been also classified into three types based on the transmission media used for the network, i.e., twisted pair cable, coaxial cable, and optical fiber cable types. The present invention relates to a transceiver for optical fiber cable, but can be connected to a conventional transceiver for coaxial cable.
Moreover, a carrier sense multiple access/collision detection (below, CSMA/CD) method is usually employed as the transmission media access method in the LAN system, and this CSMA/CD method has three states regarding the transmission in the network, i.e., "idle" state, "busy" state, and "collision" state.
In this method, a station at which a "request to send" has been generated, first supervises a common transmission line (path) and then determines whether or not another station is transmitting. This is performed by "carrier sensing". When the common path is in a "busy" state, the station waits for transmission of the data frame, but when the common path is in an "idle" state, the station transmits the frame to the common path.
In this case, since a propagation delay time occurs at the transmission of the frame, when the transmission is performed only by a detection of an "idle" state at the common path in each station, collisions of the frame occur with a plurality of stations simultaneously transmit the frame to the common path when each station detects an "idle" state at the common path. Accordingly, the normal frame can not be transmitted to the other party.
When these collision occur in the common path, in order to shorten the time for which the common path is occupied by the collision frame, each station looks for an existence of a collision when the data is under transmission. When a collision is detected, the transmission is stopped, and after waiting for a predetermined time, the same procedure is repeated in order to retransmit the frame.
The IEEE regulation 802.3 is one of the standards defined and recommended by the IEEE Standard Board for the LAN system. This standard defines various elements such as, (1) physical conditions, (2) electrical conditions, (3) communication means, and (4) network structure for the LAN system using a coaxial cable. That is, when a coaxial cable is used as the common path, the transceiver must comply with the IEEE regulation 802.3 for the LAN system.